I have some questions related to JSON serialization using Jackson in a project where I use Spring Boot 2.0.0.M6
, Spring Framework 5.0.1.R
I solve using this aproach:
ObjectMapper objectMapper = new ObjectMapper();
JavaTimeModule module = new JavaTimeModule();
module.addSerializer(Instant.class, new InstantSerializerWithMilliSecondPrecision());
objectMapper.registerModule(module);
And for InstantSerializerWithMilliSecondPrecision i used this:
public class InstantSerializerWithMilliSecondPrecision extends InstantSerializer {
public InstantSerializerWithMilliSecondPrecision() {
super(InstantSerializer.INSTANCE, false, new DateTimeFormatterBuilder().appendInstant(3).toFormatter());
}
}
Now the Instant serialization always includes milliseconds. Example: 2019-09-27T02:59:59.000Z
Solve it by using custom serializers for LocalDateTime and ZonedDateTime classes.
My solution works for me because I use only these two classes in API responses to represent date and time! I don't use Instant or Date so pay attention on it.
@Configuration
class JacksonConfig {
@Bean
fun objectMapper(): ObjectMapper {
val mapper = ObjectMapper()
val javaTimeModule = JavaTimeModule().apply {
addSerializer(LocalDateTime::class.java, KeepMillisecondLocalDateTimeSerializer())
addSerializer(ZonedDateTime::class.java, KeepMillisecondZonedDateTimeSerializer())
}
mapper.registerModule(javaTimeModule)
return mapper
}
class KeepMillisecondZonedDateTimeSerializer : JsonSerializer<ZonedDateTime>() {
private val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSX")
@Throws(IOException::class)
override fun serialize(
value: ZonedDateTime,
jsonGenerator: JsonGenerator,
serializerProvider: SerializerProvider?
) {
jsonGenerator.writeString(formatter.format(value))
}
}
class KeepMillisecondLocalDateTimeSerializer : JsonSerializer<LocalDateTime>() {
private val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS")
@Throws(IOException::class)
override fun serialize(
value: LocalDateTime,
jsonGenerator: JsonGenerator,
serializerProvider: SerializerProvider?
) {
jsonGenerator.writeString(formatter.format(value))
}
}
}
There appears to be a Jackson issue open for this here*. That link contains two workarounds
Workaround 1
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JavaTimeModule());
SimpleModule module = new SimpleModule();
module.addSerializer(ZonedDateTime.class, new JsonSerializer<ZonedDateTime>() {
@Override
public void serialize(ZonedDateTime zonedDateTime, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
jsonGenerator.writeString(DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZZZ").format(zonedDateTime));
}
});
objectMapper.registerModule(module);
objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
Workaround 2
JavaTimeModule javaTimeModule = new JavaTimeModule();
javaTimeModule.addSerializer(ZonedDateTime.class,
new ZonedDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSX")));
ObjectMapper mapper = new ObjectMapper().registerModule(javaTimeModule);
*Link is dead because they deprecated FasterXML/jackson-datatype-jsr310 and moved it to jackson-modules-java8. See https://github.com/FasterXML/jackson-modules-java8/issues/76
None of two workarounds mentioned by Sean Carroll works me. I end up with writing my own serializer for Instant.
final ObjectMapper mapper = new ObjectMapper();
final JavaTimeModule javaTimeModule = new JavaTimeModule();
javaTimeModule.addSerializer(Instant.class, new KeepMillisecondInstantSerializer());
mapper.registerModule(javaTimeModule);
public class KeepMillisecondInstantSerializer extends JsonSerializer<Instant> {
private final DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSX")
.withZone(ZoneId.of("UTC"));
@Override
public void serialize(final Instant instant, final JsonGenerator jsonGenerator, final SerializerProvider serializerProvider) throws IOException {
final String serializedInstant = dateTimeFormatter.format(instant);
jsonGenerator.writeString(serializedInstant);
}
}
I guess Jackson use Instant.toString() method to serialize Instant objects by default. I also find some discussions about Instant.toString() method on StackOverflow.
Rather than fixing the bug of Jackson library, following could be a quick work around: Create a string variable in the POJO class where you have Timestamp variable:
private Timestamp createTimeStamp;
private String stringCreateTimeStamp;
capture timestamp value as a string:
listOfPojo.forEach(pojo-> {
pojo.setStringCreateTimeStamp(request.getcreateTimeStamp().toString());
});
Refer https://www.baeldung.com/java-string-to-timestamp for conversions